Embed colors in strings

TopydoString is a string descendent that maintains information where
colors should be applied in a string. A user interface can pass a
function that transforms a color to a color representation that is
relevant there. That way, the topydo library does not make any
assumptions anymore on where colors should be applied.

topydo/lib/PrettyPrinter.py

@@ -16,6 +16,7 @@
 
 from topydo.lib.prettyprinters.Colors import PrettyPrinterColorFilter
 from topydo.lib.prettyprinters.Numbers import PrettyPrinterNumbers
+from topydo.lib.TopydoString import TopydoString
 
 
 class Printer(object):
@@ -68,7 +69,11 @@ class PrettyPrinter(Printer):
         for ppf in self.filters:
             todo_str = ppf.filter(todo_str, p_todo)
 
-        return todo_str
+        # transform color annotations to ANSI codes
+        if isinstance(todo_str, TopydoString):
+            return todo_str.with_colors(lambda c: c.as_ansi())
+        else:
+            return todo_str
 
 
 def pretty_printer_factory(p_todolist, p_additional_filters=None):

topydo/lib/TopydoString.py

+# Topydo - A todo.txt client written in Python.
+# Copyright (C) 2016 Bram Schoenmakers <me@bramschoenmakers.nl>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+""" This module provides TopydoString to embed colors in a string. """
+
+import collections
+
+class TopydoString(collections.UserString):
+    """
+    Represents a string that also contains color information. A combination of
+    (position, color) is maintained, where the position is the start position
+    where a certain color should start.
+    """
+
+    def __init__(self, p_content):
+        super().__init__(p_content)
+        self.colors = {}
+
+    def append(self, p_string, p_color):
+        """ Append a string with the given color. """
+        self.colors[len(self.data)] = p_color
+        self.data += p_string
+
+    def set_color(self, p_pos, p_color):
+        """ Start using a color at the given position. """
+        self.colors[p_pos] = p_color
+
+    def with_colors(self, p_transform_fn):
+        """
+        Returns a string with color information at the right positions.
+        p_transform_fn is a function that takes a Color object and returns a
+        string representing the color (e.g. "#ff0000").
+        """
+        result = self.data
+
+        for pos, color in sorted(self.colors.items(), reverse=True):
+            result = result[:pos] + p_transform_fn(color) + result[pos:]
+
+        return result

topydo/lib/prettyprinters/Colors.py

@@ -21,6 +21,7 @@ import re
 from topydo.lib.Color import Color
 from topydo.lib.Config import config
 from topydo.lib.PrettyPrinterFilter import PrettyPrinterFilter
+from topydo.lib.TopydoString import TopydoString
 
 
 class PrettyPrinterColorFilter(PrettyPrinterFilter):
@@ -33,35 +34,27 @@ class PrettyPrinterColorFilter(PrettyPrinterFilter):
     def filter(self, p_todo_str, p_todo):
         """ Applies the colors. """
         if config().colors():
+            p_todo_str = TopydoString(p_todo_str)
+
             priority_color = config().priority_color(p_todo.priority())
-            project_color = config().project_color()
-            context_color = config().context_color()
-            metadata_color = config().metadata_color()
-            link_color = config().link_color()
             neutral_color = Color('NEUTRAL')
 
-            # color projects / contexts
-            p_todo_str = re.sub(
-                r'\B(\+|@)(\S*\w)',
-                lambda m: (
-                    context_color.as_ansi() if m.group(0)[0] == "@"
-                    else project_color.as_ansi()) + m.group(0) + priority_color.as_ansi(),
-                p_todo_str)
-
-            # tags
-            p_todo_str = re.sub(r'\b\S+:[^/\s]\S*\b',
-                                metadata_color.as_ansi() + r'\g<0>' + priority_color.as_ansi(),
-                                p_todo_str)
+            colors = [
+                (r'\B@(\S*\w)', config().context_color()),
+                (r'\B\+(\S*\w)', config().project_color()),
+                (r'\b\S+:[^/\s]\S*\b', config().metadata_color()),
+                (r'(^|\s)(\w+:){1}(//\S+)', config().link_color()),
+            ]
 
-            # add link_color to any valid URL specified outside of the tag.
-            p_todo_str = re.sub(r'(^|\s)(\w+:){1}(//\S+)',
-                                r'\1' + link_color.as_ansi() + r'\2\3' + priority_color.as_ansi(),
-                                p_todo_str)
+            for pattern, color in colors:
+                for match in re.finditer(pattern, p_todo_str.data):
+                    p_todo_str.set_color(match.start(), color)
+                    p_todo_str.set_color(match.end(), priority_color)
 
-            p_todo_str += neutral_color.as_ansi()
+            p_todo_str.append('', neutral_color)
 
             # color by priority
-            p_todo_str = priority_color.as_ansi() + p_todo_str
+            p_todo_str.set_color(0, priority_color)
 
         return p_todo_str